Method of distilling solid carbonizable material



Nov. 1, 1932.. NlELSEN ET AL 1,886,354)

METHOD OF DISTILLING SOLID QARBONIZABLE MATERIAL Filed Feb. 17. 1927Patented Nov. 1, 1932 UNITED STATES PATENT OFFICE HAEALD NIELSEN", OFMUSWELL HILL, AND BRYAN LAING; OF HATFIELD, ENG-LAND METHOD OFDISTILLING SOLID GAEIBONIZABLE MATERIAL Application filed February 17,1927, Serial No.

This invention relates to processes for the distillation of raw solidcarbonaceous materials such as coal, lignite, brown coal, peat, wood,and shale' (hereinafter called raw solid carbonaceous materials)involving the use of a non-oxidizing gas such as producer or water gas,said gas as it is generated in the producer being withdrawn therefromand after, if necessary being superheated, being passed through acontiguous revolving retort in direct contact with carbonaceousmaterials such as raw coal so as to utilize the socalled sensible heatof the producer or water gas for the purpose of distilling off at low1:, or moderate temperatures from therawcarbonaceous materials passingthrough the retort the volatilizable and condensable oils containedtherein, the inert heating gas containing the volatilized oils beingsubsequently passed through condensers, scrubbers, oil washer, etc., forthe purpose of condensing and recovering in liquid form the saidcondensable oils. The aforesaid low temperature process also results inthe production of a semi-coke which is readily combustible and whichcan, therefore, be employed in domestic fire grates in lieu of ordinaryraw coal, and a portion of this semi-coke is usually fed into theproducer and employed in I conjunction with air or with air and steam,

for the purpose of producing either the proi ducer or the water gaswhose sensible heat is employed as the distilling medium within theretort. The combined retort and water or producer gas which remainsafter the oils have been condensed therefrom is a rich gas suitableforilluminating purposes.

The semi-coke, however, which is obtained from the retort contains aconsiderable volume of permanent gases, which gases, if the material isburnt in a fire grate are wasted so far as heating purposes areconcerned, while furthermore, a smaller and less rich volume of combinedretort and producer gases is obtained by the retorting process than169,123,and in Great Britain March 6, 1926.

'of condensable oils in their so-called primary or uncracked state, alsoto distil 01f from the raw coal or like carbonaceous material themaximum volume of permanent gases contained therein, so as both toincrease the volume of and also to enrich the gases which remain afterthe oils have been condensed therefrom and thus to produce a high gradeand high calorific gas suitable for use as socalled town or illuminatinggas.

According to the present invention the dis tillation of the solidcarbonaceous" materials is effected'by means of a combustible as, suchas water or producer gas, which, a ter being superheated if necessary,is passed through an apparatus such as a retort or a two-stage retort,in contact with the raw carbonaceous materials so that the so-calledsensible heat of the distilling medium is employed first to distil offthe volatilizable and condensable oils contained therein and thereafterto drive off the so-called' permanent gases, the temperature zones,throughout the length of the retort, being graduated so that the saidoils are distilled off at the temperatures at which they volatilize andare then withdrawn from the apparatus either at one end or preferably atdifferent points along the length thereof and at temperatures at whichno cracking can occur, while the volume of combustible gas whosesensible heat is employed as thedistilling medium is so controlled as tolower the vapor pressure of a contlnuous manner first to a process ofdistillation at low or moderate temperature so as to drive off thevolatilizable oils and then to a process of high temperaturedistillation so as to drive off the permanent gases and we have foundthat it is essential in order to ob tain a freely burning solidcarbonaceous residuum that the volatilizable oils should be withdrawnfrom theretort without cracking as otherwisegraphitic carbon isdeposited on the solid material which coats the microscopic andsub-microscopic cells and cell walls w th a highly impervious carbonfilmwhich is difficult to oxidize and whichv reduces to a marked degree thereadiness to combustibllity as well as to reactivity of the resultantfuel. It is also essential that the oil yieldlng and volatilizableconstituents should be expelled from the solid material at as. low atemperature as possible, that is to say, attemperatures ranging from 185to 580 C. while the expelling of the so-called permanent gases from thesolid material should then \take place at from 580 up to approximately1200 C. A suitable temperature range from the inlet to the outlet end ofthe retort can be maintained so as to efi'ect the aforesaid result inthe same retort. In order that the said invention may be clearlyunderstood and readily carried into efiect, the same'will now bedescribed more fully with reference to the ac companying drawing whichillustrates diagrammatically the layout of a plant constructed accordingto the present invention and in which:

A is a hopper or container for the raw material B, which is fed into theretort or rotary drum C. a is a pipe by means of which the raw materialis fed from the hopper A into the retort C, the pipe a also serving toconduct the mixed producer gas and retort gases away from the retort C.c is a fixed annular casing surrounding one end of the retort andwherein the coked fuel which is treated in the retort is collected afterfalling through the opening 0. 0 is the coke offtake which is controlledby a discharge valve, not shown, from the retortC. E is a gas producer,the producer gas from which is employed for treating the materialundergoing distillation in the retort C. -e is a pipe through which theproducer gas is drawn from the producer on its way to the retortC. Theproducer gas may be fed through regen erators (not shown) so't'hat itstemperature is raised from 1000 C. to 1200- C. so that it enters unburntinto the retort C. or the gas may beburnt in a combustion chamber 6after it leaves the producer and before passing the valve 6 The valve 6controls the quantity of producer gas supplied to the retort C. F is acondenser for the mixed gases which leave the retort C, and G is anabsorption apparatus for therecovery from the said mixed gases ofcondensable and absorbable hydrocarbon products contained therein.

The pipe 71 conducts the stripped gases from the absorption apparatus Gto an ammoma absorber I.

The raw solid carbonaceous material WlllCh is to be distilled enters theretort from the hopper A, while the hot gas from the producer which maybe burnt in the combustion chamber 6 enters the retort in the form of acontinuously flowing stream at a temperature of from 1000 C. to 1200 C.Consequently, the solid carbonaceous mater1al which is to be distilledand the hot distilling medium pass in contrafiow to one another. Thecontrolled volume of the hot gas first meets the solid carbonaceousresidue from which the oil Vapors have been driven ofi further along theretort at temperatures ranging from 185 to 580 C. The hot gas,

therefore, after entering the retort first dis-' tils off from thematerial which it encounters and at high temperatures the so-called'permanent gases are cooled down to a temperature of approximately 580C. Thereafter it drives off from the carbonaceous material the oilbearing constituents and is cooled down t9 approximately 185 C. Astheheating medium flows in countercurrent to the raw carbonaceousmaterials, the oil bearing constituents are prevented from passing intohotter zones and are carried away from the retort through, the pipe a tothe condenser F, the absorption apparatus G and the ammonia absorber I.If desired two retorts may be employed and placed in communication withone another in any suitable manner, the volatilizable'oils beingdistilled oif in a retort having a progressive temperature range of from185 to 580 C. and thereafter the solid material being passed into asecond retort, where the gaseous hydrocarbons are ClI'lVGILOfi attemperatures from 580 up to 1200 C. The inert heating gas can, if neces:sary, or desired, be superheated before being passed into the secondhigh temperature retort or before entering the high temperature zones ofthe single long retort; or the distilling gaseous medium at suitablehigh temperatures can be by-passed and admitted at different pointsalong the length of the retort. By carrying on the process in theaforesaid manner we have found that tempera- .tures up to and exceeding1100 C. may be employed after the condensable 7 oils have been drivenofi' by an inert heating medium and removed in unifiow with the heatingmedium so as to drive off the residual gaseous volatile matters, andreduce the volatile matter in the solid residuum to about 1%, thisresult being obtained without in any way interfering with the easyignitibility, combustibility or reactivity of the solid residue. 7 Thesolid resdue can, as aforesaid be burnt in open domestic grates; and ismore read ly ignltible than the ordinary semi-coke obta ned by any ofthe usual processes of low temperature distillation and far more readilycombustible than ordinary gas coke or coke oven coke. This property ofthe solid carbonaceous material obtained by the aforesaid process apofraw material at this temperature were zpears to be due to the fact thatthe original cell structure of the raw material is left intact, and thedepositing of a carbon film on the residual fuel is avoided, while thethinness of the cell walls is maintained so that a very largesuperficial surface is made available for attack by oxygen eithercombined or in a free state.

Wehave also found, that a fusible or cok ing coal, which on distillationpasses through a so-called plastic state, can be given the same degreeof reactivity, etc. as a so-called noncaking or non-coking coal, that isto say, be made to retain its original cell structure by being subjectedto a preliminary heat treatmentby gases containing suflicient oxidizingconstituents, free oxygen and the like and to an extent which will stopfusing and ag-- glomeration.

For example a bituminous coal was distilled by means of an inert gaseousheating medium in a rotary retort, the raw coal having a volatilecontent of 30%. It wasv observed that oil began to distill oil at 210 C.together with a small volume of gas and at 570 C. all the oil yieldingconstituents or condensable hydrocarbons were removed from the materialunder distillation.

The quantity of products obtained per ton (570 C.)

20 gallons of oil.

15 gallons of ammoniacal liquor,

2,500 cubic feet of gas. The volatile matter still present in the solidmaterial was reduced to 10%.

When this material passed into the next zone and was subjected to atemperature of 950 C. the volatile matters were expelled in the form ofgas, and a volume of about 5000 cubic feet was obtained, the gasconsisting mainly of hydrogen, methane and carbon monoxide. Only 1.5% to2% of volatile matter was left in the resultant fuel or coke after beingsubjected to this. second treatment at temperatures upto 950 (1, and itwas found possible to ignite the coke by means of paper only in anordinary open domestic grate.

Microscopical research showed that no deposit of graphitic carbon waspresent.

It was also found that on account of the fact that cracking did not takeplace owing to the oil yielding volatilizable constituents being carriedoff in unifiow with the heating gases a primary oil was obtainedcontaining a large percentage of the more valuable high boilingfractions or lubricating oils rich in hydrogen.

By the present method it is possible therefore to produce from solidcarbonaceous ma way interfering with the reactivity or combustibility ofthe solid residue, or in other words, to produce so-called hightemperature coke with a reactivity, v ignitibility, equal to, if notsuperior to, socalled low temperature coke, together with the largestpossible yield of liquid and gaseous hydrocarbons in their most valuablestate.

As the resultant fuel is exceedingly reactive and easily oxidized,either by free oxygen or combined oxygen such" as is present in metallicores, such as iron or copper oxides, and the like, or in steam, it is ofgreater value for domestic use or industrial processes than thecomparatively speaking non-reactive carbon. material hitherto used withscant success only.

The resultant coke is friable and after crushing is eminently suitablefor use as a powdered fuel owing to its high degree of reactivity andfree burning properties.

What We do claim as our invention anddesire to secure by Letters Patentis 1. A method of distilling raw, solid, distillcombustibility and ableand carbonizable material, which comprises passing the raw material tobe distilled in a continuous manner through a retort, admitting to theretort, at a temperature of approximately 1200 C., a controlled volumeof a heated non-oxidizing gas, and passing the heated gas in the form ofa continuously flowing stream through the retort in counter flow to thecarbonizable material passing therethrough, so that the sensible heat ofthe heating gas is utilized both for the purpose of expelling from thematerial, at low temperatures, in vapor form, the oil yieldingconstituents and carrying the same into cooler zones in uniflow with theheating gas, and also for expelling at a higher temperature, gaseoushydi'ocarbons contained'in the solid residue remaining after the oilshave been expelled, whereby the coke formed contains from 1.5% to 2%volatile matter.

2. A method of distilling raw, solid, distillable and carbonizablematerial with byproduct recovery, which comprises passing the materialin thin, continuously moving, layers in contraflow to and in contactwith a heated non-oxidizing gas, the volume of heated gas employed asthe distilling medium being so controlled as to lower the partialpressure of the volatilizable oils as much as possible, the materialbeing first subjected toa process of low temperature distillation, at atemperature not exceeding approximately 580 6., whereby oil in vaporform will be obtainedat temperatures at which no cracking can occur,said oil vapors being carried in suspension in the heating gas intocooler zones, and subjecting to high temperature distillation by directcontact with the heating gas at temperatures ranging from approximately580 C. to approximately 1200 C. the solid residue that has been freedfrom oil to drive off gaseous hydrocarbons contained in said residue,the same heating gas being employed for both the high and lowtemperature distillation processes, whereby the coke formed contains 1.5to 2% volatile matter.

HA-RALD NIELSEN.

BRYAN LAING.

